Issue 116 Approving and calibrating Metering Systems for Settlement purposes

Code of Practice (CoP) 1: ‘The Metering of Circuits with a Rated Capacity Exceeding 100 MVA for
Settlement Purposes’ and CoP2: ‘The Metering of Circuits with a Rated Capacity not Exceeding 100
MVA for Settlement Purposes’ currently refer only to the inductive Current Transformers (CTs) and
Voltage Transformers (VTs) of the 61869 series of standards.

However, CoPs 1 and 2 also contain a clause (in 5.1 ‘Metering Equipment’) that allows for individual
items of Metering Equipment to be combined to perform the same task, provided ‘the requirements’ of
the relevant CoP are met.

It is unclear if other types of equipment like Low Power Instrument Transformers (LPITs) could be used
as part of a combination of Metering Equipment that would constitute a Metering System.
Enabling this would allow manufacturers to develop innovative Metering Systems.

LPITs can provide the following benefits compared to conventional CT/VTs:

• Small and light weight: a major benefit especially for Offshore substations
• Improved personal safety: no dangerous voltages if the secondary winding of the current
  measuring element is left ‘open-circuit’
• Accurate at harmonics
• Very good linearity: convenient calibration at low voltage and current test points